GLSL Specification 3.30.6.Clean

8/12/2019 GLSL Specification 3.30.6.Clean

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The OpenGLShading Language

Language Version: 3.30

Document Revision: 6

11-Mar-2010

Editor: John Kessenich, Intel

Version 1.1 Authors: John Kessenich, Dave Baldwin, Randi Rost


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Copyright (c) 2008-2010 The Khronos Group Inc. All Rights Reserve.

This speci!ic"tion is protecte #y copyright l"$s "n cont"ins %"teri"l propriet"ry to the Khronos Group&Inc. It or "ny co%ponents %"y not #e reprouce& repu#lishe& istri#ute& tr"ns%itte& ispl"yero"c"st or other$ise e'ploite in "ny %"nner $ithout the e'press prior $ritten per%ission o! KhronosGroup. ou %"y use this speci!ic"tion !or i%ple%enting the !unction"lity therein& $ithout "ltering orre%oving "ny tr"e%"r& copyright or other notice !ro% the speci!ic"tion& #ut the receipt or possession o!this speci!ic"tion oes not convey "ny rights to reprouce& isclose& or istri#ute its contents& or to%"nu!"cture& use& or sell "nything th"t it %"y escri#e& in $hole or in p"rt.

Khronos Group gr"nts e'press per%ission to "ny current *ro%oter& Contri#utor or Aopter %e%#er o!Khronos to copy "n reistri#ute +,/II/ versions o! this speci!ic"tion in "ny !"shion& provie th"t, CARG is %"e !or the speci!ic"tion "n the l"test "v"il"#le up"te o! the speci!ic"tion !or "nyversion o! the A*I is use $henever possi#le. 3uch istri#ute speci!ic"tion %"y #e re-!or%"tte A34,G A3 the contents o! the speci!ic"tion "re not ch"nge in "ny $"y. The speci!ic"tion %"y #eincorpor"te into " prouct th"t is sol "s long "s such prouct inclues signi!ic"nt inepenent $orevelope #y the seller. A lin to the current version o! this speci!ic"tion on the Khronos Group $e#-siteshoul #e inclue $henever possi#le $ith speci!ic"tion istri#utions.

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Khronos& penK/& penKG3& pen6G& penA7& pen34 3 "n pen "re tr"e%"rs o!the Khronos Group Inc. C44A/A is " tr"e%"r o! 3ony Co%puter ntert"in%ent Inc. use #yper%ission #y Khronos. penG4 "n pen4 "re registere tr"e%"rs "n the penG4 3 logo is "tr"e%"r o! 3ilicon Gr"phics Inc. use #y per%ission #y Khronos. All other prouct n"%es& tr"e%"rs&"n9or co%p"ny n"%es "re use solely !or ienti!ic"tion "n #elong to their respective o$ners.

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Table of Contents

1 Introduction.................................................................................................................................1

1.1 Acknowledgents................................................................................................................11.! "hanges ............................................................................................................................... 1

1.!.1 #uar$ o% "hanges %ro Version 1.&'..................................................................... 11.( )verview.............................................................................................................................. !1.* Error +andling......................................................................................................................!1.& $-ogra-hical "onventions................................................................................................. !1. De-recation.......................................................................................................................... !

! )verview o% )-en/0 #hading....................................................................................................(!.1 Verte 2rocessor.................................................................................................................. (!.! /eoetr$ 2rocessor............................................................................................................. (!.( 3ragent 2rocessor.............................................................................................................. (

( Basics.......................................................................................................................................... &(.1 "haracter #et........................................................................................................................ &(.! #ource #trings...................................................................................................................... &(.( 2re-rocessor......................................................................................................................... (.* "oents.......................................................................................................................... 11(.& okens................................................................................................................................ 1!(. Ke$words............................................................................................................................1!(.4 Identi%iers........................................................................................................................... 1*(.5 #tatic 6se........................................................................................................................... 1*

* Varia7les and $-es..................................................................................................................1&*.1 Basic $-es........................................................................................................................ 1&

*.1.1 Void............................................................................................................................ 15*.1.! Booleans..................................................................................................................... 15*.1.( Integers....................................................................................................................... 15*.1.* 3loats.......................................................................................................................... !'*.1.& Vectors........................................................................................................................!1*.1. 8atrices...................................................................................................................... !1*.1.4 #a-lers..................................................................................................................... !1*.1.5 #tructures....................................................................................................................!!*.1.9 Arra$s......................................................................................................................... !(*.1.1' I-licit "onversions................................................................................................ !&

*.! #co-ing...............................................................................................................................!&

*.( #torage uali%iers...............................................................................................................!4*.(.1 De%ault #torage uali%ier............................................................................................!5*.(.! "onstant uali%ier...................................................................................................... !5*.(.( "onstant E-ressions................................................................................................. !5*.(.* In-uts.......................................................................................................................... !9*.(.& 6ni%or...................................................................................................................... ('

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*.(. )ut-uts....................................................................................................................... (1*.(.4 Inter%ace Blocks..........................................................................................................(!*.(.5 0a$out uali%iers........................................................................................................(&

*.(.5.1 In-ut 0a$out uali%iers.......................................................................................(&*.(.5.! )ut-ut 0a$out uali%iers.................................................................................... (5*.(.5.( 6ni%or Block 0a$out uali%iers.......................................................................(9

*.(.9 Inter-olation................................................................................................................*1*.(.9.1 Redeclaring Built;in Inter-olation Varia7les in the "o-ati7ilit$ 2ro%ile.........*!

*.* 2araeter uali%iers...........................................................................................................*!*.& 2recision and 2recision uali%iers..................................................................................... *(

*.&.1 Range and 2recision................................................................................................... *(*.&.! 2recision uali%iers.................................................................................................... *(*.&.( De%ault 2recision uali%iers....................................................................................... *(*.&.* Availa7le 2recision uali%iers....................................................................................**

*. Variance and the Invariant uali%ier.................................................................................. ***..1 he Invariant uali%ier............................................................................................... *&*..! Invariance o% "onstant E-ressions........................................................................... *

*.4 )rder o% uali%ication........................................................................................................ *& )-erators and E-ressions........................................................................................................*4

&.1 )-erators............................................................................................................................ *4&.! Arra$ )-erations............................................................................................................... *5&.( 3unction "alls.................................................................................................................... *5&.* "onstructors....................................................................................................................... *5

&.*.1 "onversion and #calar "onstructors.......................................................................... *5&.*.! Vector and 8atri "onstructors................................................................................. *9

&.*.( #tructure "onstructors................................................................................................&1&.*.* Arra$ "onstructors..................................................................................................... &!

&.& Vector "o-onents............................................................................................................&!&. 8atri "o-onents............................................................................................................&*&.4 #tructure and Arra$ )-erations..........................................................................................&*&.5 Assignents....................................................................................................................... &&&.9 E-ressions........................................................................................................................ &&.1' Vector and 8atri )-erations..........................................................................................&9

#tateents and #tructure...........................................................................................................1.1 3unction De%initions...........................................................................................................!

.1.1 3unction "alling "onventions....................................................................................(

.! #election.............................................................................................................................&.( Iteration.............................................................................................................................. .* Ju-s..................................................................................................................................4

4 Built;in Varia7les......................................................................................................................54.1 Verte and /eoetr$ #hader #-ecial Varia7les................................................................ 5

4.1.1 "o-ati7ilit$ 2ro%ile Verte and /eoetr$ #hader #-ecial Varia7les..................... 4'

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1 Introduction

his docuent s-eci%ies onl$ version (.(' o% the )-en/0 #hading 0anguage. It re=uires >>VER#I)>

to su7stitute ((', and re=uires #versionto acce-t onl$ (('. I% #version is declared with a saller

nu7er, the language acce-ted is a -revious version o% the shading language, which will 7e su--orted

de-ending on the version and t$-e o% contet in the )-en/0 A2I. #ee the )-en/0 /ra-hics #$ste

#-eci%ication, Version (.(, %or details on what language versions are su--orted.

All )-en/0 /ra-hics #$ste #-eci%ication re%erences in this s-eci%ication are to version (.(.

1.1 Acknowledgments

his s-eci%ication is 7ased on the work o% those who contri7uted to -ast versions o% the )-en/00anguage #-eci%ication, the )-en/0 E# !.' 0anguage #-eci%ication, and the %ollowing contri7utors to

this version:

2at Brown,


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1 Introduction

0a$out =uali%iers can declare the location o% %ragent shader out-uts.

Add ARB>shader>7it>encoding etension:

3loating;-oint varia7les within a shader are encoded according to IEEE 4&*.

Add 7uilt;in %unctions converting %loating;-oint values to and %ro signed or unsigned

integers re-resenting their encoding.

"hange #line7ehavior: he nu7er -rovided is the nu7er o% the net line o% code, not the

current line. his akes it atch " seantics.

"lari%$ that the second co-onent o%Pis unused %or 1Dshadow looku-s.

1." O#er#ie$

his docuent descri7es The Oen!L "ha#ing Language$ version 3.30.

Inde-endent co-ilation units written in this language are calledsha#ers. Arogramis a co-lete set o%

shaders that are co-iled and linked together. he ai o% this docuent is to thoroughl$ s-eci%$ the-rograing language. he )-en/0 /ra-hics #$ste #-eci%ication will s-eci%$ the )-en/0 entr$

-oints used to ani-ulate and counicate with -rogras and shaders.

1.% &rror 'andling

"o-ilers, in general, acce-t -rogras that are ill;%ored, due to the i-ossi7ilit$ o% detecting all ill;

%ored -rogras. 2orta7ilit$ is onl$ ensured %or well;%ored -rogras, which this s-eci%ication

descri7es. "o-ilers are encouraged to detect ill;%ored -rogras and issue diagnostic essages, 7ut are

not re=uired to do so %or all cases. "o-ilers are re=uired to return essages regarding leicall$,

graaticall$, or seanticall$ incorrect shaders.

1. Typographical Con#entionsItalic, 7old, and %ont choices have 7een used in this s-eci%ication -riaril$ to i-rove reada7ilit$. "ode

%ragents use a %ied width %ont. Identi%iers e7edded in tet are italici?ed. Ke$words e7edded in tet

are 7old. )-erators are called 7$ their nae, %ollowed 7$ their s$7ol in 7old in -arentheses. he

clari%$ing graar %ragents in the tet use 7old %or literals and italics %or non;terinals. he o%%icial

graar in section 9 #hading 0anguage /raarC uses all ca-itals %or terinals and lower case %or

non;terinals.

1.( )eprecation

2revious versions o% the )-en/0 #hading 0anguage de-recated soe %eatures. hese are clearl$ called

out in this s-eci%ication as de-recatedC. he$ are still -resent in this version o% the language, 7ut are

targeted %or -otential reoval in a %uture version o% the shading language. he )-en/0 A2I has a

%orward co-ati7ilit$ ode that will disallow use o% de-recated %eatures. I% co-iling in a ode where

use o% de-recated %eatures is disallowed, their use causes co-ile tie errors. #ee the )-en/0 /ra-hics

#$ste #-eci%ication %or details on what causes de-recated language %eatures to 7e acce-ted or to return

an error.

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2 O#er#ie$ of OpenGL Shading

he )-en/0 #hading 0anguage is actuall$ several closel$ related languages. hese languages are used

to create shaders %or each o% the -rograa7le -rocessors contained in the )-en/0 -rocessing -i-eline.

"urrentl$, these -rocessors are the verte, geoetr$, and %ragent -rocessors.

6nless otherwise noted in this -a-er, a language %eature a--lies to all languages, and coon usage will

re%er to these languages as a single language. he s-eci%ic languages will 7e re%erred to 7$ the nae o%

the -rocessor the$ target: verte, geoetr$, or %ragent.

8ost )-en/0 state is not tracked or ade availa7le to shaders. $-icall$, user;de%ined varia7les will 7e

used %or counicating 7etween di%%erent stages o% the )-en/0 -i-eline. +owever, a sall aount o%

state is still tracked and autoaticall$ ade availa7le to shaders, and there are a %ew 7uilt;in varia7les %orinter%aces 7etween di%%erent stages o% the )-en/0 -i-eline.

2.1 Verte* +rocessor

he verte% rocessoris a -rograa7le unit that o-erates on incoing vertices and their associated data.

"o-ilation units written in the )-en/0 #hading 0anguage to run on this -rocessor are called verte%

sha#ers. hen a co-lete set o% verte shaders are co-iled and linked, the$ result in a verte% sha#er

e%ecuta&'ethat runs on the verte -rocessor.

he verte -rocessor o-erates on one verte at a tie. It does not re-lace gra-hics o-erations that re=uire

knowledge o% several vertices at a tie.

2.2 Geometry +rocessorhegeometr( rocessor is a -rograa7le unit that o-erates on data %or incoing vertices %or a -riitive

asse7led a%ter verte -rocessing and out-uts a se=uence o% vertices %oring out-ut -riitives.

"o-ilation units written in the )-en/0 #hading 0anguage to run on this -rocessor are calledgeometr(

sha#ers. hen a co-lete set o% geoetr$ shaders are co-iled and linked, the$ result in ageometr(

sha#er e%ecuta&'e that runs on the geoetr$ -rocessor.

A single invocation o% the geoetr$ shader eecuta7le on the geoetr$ -rocessor will o-erate on a

declared in-ut -riitive with a %ied nu7er o% vertices. his single invocation can eit a varia7le

nu7er o% vertices that are asse7led into -riitives o% a declared out-ut -riitive t$-e and -assed to

su7se=uent -i-eline stages.

2." ,ragment +rocessorhe)ragment rocessoris a -rograa7le unit that o-erates on %ragent values and their associated

data. "o-ilation units written in the )-en/0 #hading 0anguage to run on this -rocessor are called

)ragment sha#ers. hen a co-lete set o% %ragent shaders are co-iled and linked, the$ result in a

)ragment sha#er e%ecuta&'ethat runs on the %ragent -rocessor.

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2 Overview of OpenGL Shading

A %ragent shader cannot change a %ragents F%,(G -osition. Access to neigh7oring %ragents is not

allowed. he values co-uted 7$ the %ragent shader are ultiatel$ used to u-date %rae7u%%er eor$

or teture eor$, de-ending on the current )-en/0 state and the )-en/0 coand that caused the

%ragents to 7e generated.

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" -asics

".1 Character Set

he source character set used %or the )-en/0 shading languages is a su7set o% A#"II. It includes the

%ollowing characters:

he letters a-z, A-Z, and the underscore F >G.

he nu7ers0-9.

he s$7ols -eriod F.G, -lus F+G, dash F-G, slash F/G, asterisk FG, -ercent F!G, angled 7rackets F"and

G, s=uare 7rackets F $and % G, -arentheses F &and 'G, 7races F (and )G, caret F*G, vertical 7ar F G,

a-ersand FG, tilde FG, e=uals FG, eclaation -oint FG, colon FG, seicolon FG, coa F,G, and=uestion ark F2G.

he nu7er sign F#G %or -re-rocessor use.

hite s-ace: the s-ace character, hori?ontal ta7, vertical ta7, %or %eed, carriage;return, and line;

%eed.

0ines are relevant %or co-iler diagnostic essages and the -re-rocessor. he$ are terinated 7$

carriage;return or line;%eed. I% 7oth are used together, it will count as onl$ a single line terination. 3or

the reainder o% this docuent, an$ o% these co7inations is si-l$ re%erred to as a new;line. here is no

line continuation character.

In general, the languageHs use o% this character set is case sensitive.

here are no character or string data t$-es, so no =uoting characters are included.

here is no end;o%;%ile character.

".2 Source Strings

he source %or a single shader is an arra$ o% strings o% characters %ro the character set. A single shader

is ade %ro the concatenation o% these strings. Each string can contain ulti-le lines, se-arated 7$ new;

lines.


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3 Basics

"." +reprocessor

here is a -re-rocessor that -rocesses the source strings as -art o% the co-ilation -rocess.

he co-lete list o% -re-rocessor directives is as %ollows.

#

#define

#undef

#if

#ifdef

#ifndef

#else

#elif

#endif

#error

#pragma

#extension

#version

#line

he %ollowing o-erators are also availa7le

defined

##

Each nu7er sign F#G can 7e -receded in its line onl$ 7$ s-aces or hori?ontal ta7s. It a$ also 7e

%ollowed 7$ s-aces and hori?ontal ta7s, -receding the directive. Each directive is terinated 7$ a new;

line. 2re-rocessing does not change the nu7er or relative location o% new;lines in a source string.

he nu7er sign F#G on a line 7$ itsel% is ignored. An$ directive not listed a7ove will cause a diagnostic

essage and ake the i-leentation treat the shader as ill;%ored.

#de3ineand #4nde3%unctionalit$ are de%ined as is standard %or " -re-rocessors %or acro de%initions

7oth with and without acro -araeters.

he %ollowing -rede%ined acros are availa7le

__LINE__

__FILE__

__VERSION__

**L+,**will su7stitute a decial integer constant that is one ore than the nu7er o% -receding new;lines in the current source string.

**+L**will su7stitute a decial integer constant that sa$s which source string nu7er is currentl$

7eing -rocessed.

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3 Basics

**VR"+O,**will su7stitute a decial integer re%lecting the version nu7er o% the )-en/0 shading

language. he version o% the shading language descri7ed in this docuent will have**VR"+O,**

su7stitute the decial integer (('.

All acro naes containing two consecutive underscores F55 G are reserved %or %uture use as -rede%ined

acro naes. All acro naes -re%ied with /0>C F/0C %ollowed 7$ a single underscoreG are also

reserved.

#i3, #i3de3, #i3nde3, #else, #eli3, and#endi3are de%ined to o-erate as is standard %or " -re-rocessors.

E-ressions %ollowing #i3and #eli3are %urther restricted to e-ressions o-erating on literal integer

constants, -lus identi%iers consued 7$ the de3inedo-erator. It is an error to use #i3 or #eli3 on

e-ressions containing unde%ined acro naes, other than as arguents to the de3ined o-erator.

"haracter constants are not su--orted. he o-erators availa7le are as %ollows.

+recedence Operator class Operators ssociati#ity

1 FhighestG -arenthetical grou-ing F G


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3 Basics

2re-rocessor e-ressions will 7e evaluated according to the 7ehavior o% the host -rocessor, not the

-rocessor targeted 7$ the shader.

#error will cause the i-leentation to -ut a diagnostic essage into the shader o7TectHs in%oration log

Fsee section .1.11 #hader and 2rogra ueriesC in the )-en/0 /ra-hics #$ste #-eci%ication %or how

to access a shader o7TectHs in%oration logG. he essage will 7e the tokens %ollowing the #error

directive, u- to the %irst new;line. he i-leentation ust then consider the shader to 7e ill;%ored.

#7ragmaallows i-leentation de-endent co-iler control. okens %ollowing #7ragmaare not su7Tect

to -re-rocessor acro e-ansion. I% an i-leentation does not recogni?e the tokens %ollowing

#7ragma, then it will ignore that -raga. he %ollowing -ragas are de%ined as -art o% the language.

#pragma ST!L

he 8D:;-raga is used to reserve -ragas %or use 7$ %uture revisions o% this language.


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3 Basics

I% the o-tionalro)i'e arguent is -rovided, it ust 7e the nae o% an )-en/0 -ro%ile. "urrentl$, there

are two choices:

%ore

%ompati$ilit&

I% noro)i'e arguent is -rovided, the de%ault is core. 6nless otherwise s-eci%ied, this s-eci%ication is

docuenting the core -ro%ile, and ever$thing s-eci%ied %or the core -ro%ile is also availa7le in the

co-ati7ilit$ -ro%ile. 3eatures s-eci%ied as 7elonging s-eci%icall$ to the co-ati7ilit$ -ro%ile are not

availa7le in the core -ro%ile.

here is a 7uilt;in acro de%inition %or each -ro%ile the i-leentation su--orts. All i-leentations

-rovide the %ollowing acro:

#define !L_%ore_profile '

I-leentations -roviding the co-ati7ilit$ -ro%ile -rovide the %ollowing acro:

#define !L_%ompati$ilit&_profile '

he #versiondirective ust occur in a shader 7e%ore an$thing else, ece-t %or coents and white s-ace.

!


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3 Basics

B$ de%ault, co-ilers o% this language ust issue co-ile tie s$ntactic, graatical, and seantic

errors %or shaders that do not con%or to this s-eci%ication. An$ etended 7ehavior ust %irst 7e ena7led.

Directives to control the 7ehavior o% the co-iler with res-ect to etensions are declared with the

#e=tensiondirective

#extension extension_name:behavior

#extension all :behavior

where e%tension*nameis the nae o% an etension. Etension naes are not docuented in this

s-eci%ication. he token alleans the 7ehavior a--lies to all etensions su--orted 7$ the co-iler. he

&ehavior can 7e one o% the %ollowing

behavior &ffect

re/uire Behave as s-eci%ied 7$ the etension e%tension*name.

/ive an error on the #e=tension i% the etension e%tension*name is notsu--orted, or i% allis s-eci%ied.

enable Behave as s-eci%ied 7$ the etension e%tension*name.

arn on the #e=tensioni% the etension e%tension*nameis not su--orted.

/ive an error on the #e=tension i% allis s-eci%ied.

$arn Behave as s-eci%ied 7$ the etension e%tension*name, ece-t issue warningson an$ detecta7le use o% that etension, unless such use is su--orted 7$ otherena7led or re=uired etensions.

I% all is s-eci%ied, then warn on all detecta7le uses o% an$ etension used.

arn on the #e=tensioni% the etension e%tension*nameis not su--orted.

disable Behave Fincluding issuing errors and warningsG as i% the etensione%tension*nameis not -art o% the language de%inition.

I% all is s-eci%ied, then 7ehavior ust revert 7ack to that o% the non;etendedcore version o% the language 7eing co-iled to.

arn on the #e=tension i% the etension e%tension*nameis not su--orted.

he e=tensiondirective is a si-le, low;level echanis to set the 7ehavior %or each etension. It does

not de%ine -olicies such as which co7inations are a--ro-riate, those ust 7e de%ined elsewhere. )rder

o% directives atters in setting the 7ehavior %or each etension: Directives that occur later override those

seen earlier. he allvariant sets the 7ehavior %or all etensions, overriding all -reviousl$ issued

e=tension directives, 7ut onl$ %or the &ehaviorswarnand disa>le.

1"


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3 Basics

he initial state o% the co-iler is as i% the directive

#extension all ( disa$le

was issued, telling the co-iler that all error and warning re-orting ust 7e done according to thiss-eci%ication, ignoring an$ etensions.

Each etension can de%ine its allowed granularit$ o% sco-e. I% nothing is said, the granularit$ is a shader

Fthat is, a single co-ilation unitG, and the etension directives ust occur 7e%ore an$ non;-re-rocessor

tokens. I% necessar$, the linker can en%orce granularities larger than a single co-ilation unit, in which

case each involved shader will have to contain the necessar$ etension directive.

8acro e-ansion is not done on lines containing #e=tensionand #versiondirectives.

#lineust have, a%ter acro su7stitution, one o% the %ollowing %ors:

#line line

#line line source-string-number

where 'ine andsource-string-num&er are constant integer e-ressions. A%ter -rocessing this directiveFincluding its new;lineG, the i-leentation will 7ehave as i% it is co-iling at line nu7er 'ineand

source string nu7ersource-string-num&er. #u7se=uent source strings will 7e nu7ered se=uentiall$,

until another #linedirective overrides that nu7ering.

".% Comments

"oents are deliited 7$ @L and L@, or 7$ @@ and a new;line. he 7egin coent deliiters F@L or @@G are

not recogni?ed as coent deliiters inside o% a coent, hence coents cannot 7e nested. I% a

coent resides entirel$ within a single line, it is treated s$ntacticall$ as a single s-ace.


18/123

3 Basics

". To0ens

he language is a se=uence o% tokens. A token can 7e

to/en:

/e(or#

i#enti)ier

integer-constant

)'oating-constant

oerator

( )

".( ey$ords

he %ollowing are the ke$words in the language, and cannot 7e used %or an$ other -ur-ose than that

de%ined 7$ this docuent:

attri>4te const 4ni3orm var?ing

la?o4t

centroid 3lat smoot@ no7ers7ective

>reak contin4e do 3or w@ile switc@ case de3a4lt

i3 else

in o4t ino4t

3loat int void >ool tr4e 3alse

invariant

discard ret4rn

mat mat< matB

mat= mat=< mat=B

matvecB

4int 4vec 4vec< 4vecB

low7 medi4m7 @ig@7 7recision

sam7ler1D sam7lerD sam7lere

sam7ler1D8@adow sam7lerD8@adow sam7lerC4>e8@adow sam7ler1DArra? sam7lerDArra?

sam7ler1DArra?8@adow sam7lerDArra?8@adow

isam7ler1D isam7lerD isam7lere

isam7ler1DArra? isam7lerDArra?

12


19/123

3 Basics

4sam7ler1D 4sam7lerD 4sam7lere

4sam7ler1DArra? 4sam7lerDArra?

sam7lerDect sam7lerDect8@adow isam7lerDect 4sam7lerDect sam7lerE433er isam7lerE433er 4sam7lerE433er

sam7lerDF8 isam7lerDF8 4sam7lerDF8

sam7lerDF8Arra? isam7lerDF8Arra? 4sam7lerDF8Arra?

str4ct

he %ollowing are the ke$words reserved %or %uture use. 6sing the will result in an error:

common 7artition active

asm

class 4nion en4m t?7ede3 tem7late t@is 7acked

goto

inline noinline volatile 74>lic static e=tern e=ternal inter3ace

long s@ort do4>le @al3 3i=ed 4nsigned s47er7

in74t o4t74t

@vec @vec< @vecB dvec dvec< dvecB 3vec 3vec< 3vecB

sam7ler


20/123

3 Basics

". Identifiers

Identi%iers are used %or varia7le naes, %unction naes, structure naes, and %ield selectors F%ield

selectors select co-onents o% vectors and atrices siilar to structure %ields, as discussed in section &.&Vector "o-onentsC and section &. 8atri "o-onentsC G. Identi%iers have the %or

i#enti)ier

non#igit

i#enti)ier non#igit

i#enti)ier #igit

non#igit: one o%

5 a > c d e 3 g @ i G k l m n o 7 H r s t 4 v w = ? z

A E C D I J : K L M N ; F O P Q R 8 S T U V W Z

#igit: one o%

0 1 < B X Y [ 9

Identi%iers starting with gl>C are reserved %or use 7$ )-en/0, and a$ not 7e declared in a shader as

either a varia7le or a %unction. +owever, as noted in the s-eci%ication, there are soe cases where

-reviousl$ declared varia7les can 7e redeclared to change or add soe -ro-ert$, and -redeclared Ugl>U

naes are allowed to 7e redeclared in a shader onl$ %or these s-eci%ic -ur-oses. 8ore generall$, it is an

error to redeclare a varia7le, including those starting gl>C.

".3 Static 4se

#oe language rules descri7ed 7elow de-end on whether soething isstatica''( written or used.

A shader contains astatic useo% Forstatic assignmenttoG a varia7le%i%, a%ter -re-rocessing, the shader

contains a stateent that would read For writeG%, whether or not run;tie %low o% control will cause that

stateent to 7e eecuted.

14


21/123

% Variables and Types

All varia7les and %unctions ust 7e declared 7e%ore 7eing used. Varia7le and %unction naes are

identi%iers.

here are no de%ault t$-es. All varia7le and %unction declarations ust have a declared t$-e, and

o-tionall$ =uali%iers. A varia7le is declared 7$ s-eci%$ing its t$-e %ollowed 7$ one or ore naes

se-arated 7$ coas. In an$ cases, a varia7le can 7e initiali?ed as -art o% its declaration 7$ using the

assignent o-erator FG. he graar near the end o% this docuent -rovides a %ull re%erence %or the

s$nta o% declaring varia7les.

6ser;de%ined t$-es a$ 7e de%ined using str4ctto aggregate a list o% eisting t$-es into a single nae.

he )-en/0 #hading 0anguage is t$-e sa%e. here are no i-licit conversions 7etween t$-es, with theece-tion that an integer value a$ a--ear where a %loating;-oint t$-e is e-ected, and 7e converted to a

%loating;-oint value. Eactl$ how and when this can occur is descri7ed in section *.1.1'I-licit

"onversionsC and as re%erenced 7$ other sections in this s-eci%ication.

%.1 -asic Types

he )-en/0 #hading 0anguage su--orts the %ollowing 7asic data t$-es, grou-ed as %ollows.

rans-arent t$-es

Type 5eaning

void %or %unctions that do not return a value

>ool a conditional t$-e, taking on values o% true or %alse

int a signed integer

4int an unsigned integer

3loat a single %loating;-oint scalar

vec a two;co-onent %loating;-oint vector

vec< a three;co-onent %loating;-oint vector

vecB a %our;co-onent %loating;-oint vector

>vec a two;co-onent Boolean vector

>vec< a three;co-onent Boolean vector

>vecB a %our;co-onent Boolean vector

ivec a two;co-onent signed integer vector

ivec< a three;co-onent signed integer vector

ivecB a %our;co-onent signed integer vector

15


22/123

4 #aria$%es and &'pes

Type 5eaning

4vec a two;co-onent unsigned integer vector

4vec< a three;co-onent unsigned integer vector4vecB a %our;co-onent unsigned integer vector

mat a !! %loating;-oint atri

mat< a (( %loating;-oint atri

matB a ** %loating;-oint atri

mat= sae as a mat

mat=< a %loating;-oint atri with ! coluns and ( rows

mat=B a %loating;-oint atri with ! coluns and * rows

mat


23/123


Type 5eaning

sam7lerDF8Arra? a handle %or accessing a !D ulti;sa-le arra$ teture

#igned Integer #a-ler $-es Fo-a=ueG

Type 5eaning

isam7ler1D a handle %or accessing an integer 1D teture

isam7lerD a handle %or accessing an integer !D teture

isam7lere a handle %or accessing an integer cu7e a--ed teture

isam7lerDect a handle %or accessing an integer !D rectangular teture

isam7ler1DArra? a handle %or accessing an integer 1D arra$ teture

isam7lerDArra? a handle %or accessing an integer !D arra$ teture

isam7lerE433er a handle %or accessing an integer 7u%%er teture

isam7lerDF8 a handle %or accessing an integer !D ulti;sa-le teture

isam7lerDF8Arra? a handle %or accessing an integer !D ulti;sa-le arra$ teture

6nsigned Integer #a-ler $-es Fo-a=ueG

Type 5eaning

4sam7ler1D a handle %or accessing an unsigned integer 1D teture

4sam7lerD a handle %or accessing an unsigned integer !D teture

4sam7lere a handle %or accessing an unsigned integer cu7e a--ed teture

4sam7lerDect a handle %or accessing an unsigned integer rectangular teture

4sam7ler1DArra? a handle %or accessing an unsigned integer 1D arra$ teture

4sam7lerDArra? a handle %or accessing an unsigned integer !D arra$ teture

4sam7lerE433er a handle %or accessing an unsigned integer 7u%%er teture

4sam7lerDF8 a handle %or accessing an unsigned integer !D ulti;sa-le teture

4sam7lerDF8Arra? a handle %or accessing an unsigned integer !D ulti;sa-le teturearra$

In addition, a shader can aggregate these using arra$s and structures to 7uild ore co-le t$-es.

here are no -ointer t$-es.

17


24/123


%.1.1 Void

3unctions that do not return a value ust 7e declared as void. here is no de%ault %unction return t$-e.

he ke$word voidcannot 7e used in an$ other declarations Fece-t %or e-t$ %oral or actual -araeter

listsG.

%.1.2 -ooleans

o ake conditional eecution o% code easier to e-ress, the t$-e >oolis su--orted. here is no

e-ectation that hardware directl$ su--orts varia7les o% this t$-e. It is a genuine Boolean t$-e, holding

onl$ one o% two values eaning either true or %alse. wo ke$words tr4eand 3alsecan 7e used as literal

Boolean constants. Booleans are declared and o-tionall$ initiali?ed as in the %ollow ea-le:

$ool su%%ess ** de%lare +su%%ess, to $e a -oolean

$ool done . false ** de%lare and initiali"e +done,

he right side o% the assignent o-erator F G ust 7e an e-ression whose t$-e is >ool.

E-ressions used %or conditional Tu-s Fi3, 3or, 2, w@ile, do-w@ileG ust evaluate to the t$-e >ool.

%.1." Integers

#igned and unsigned integer varia7les are %ull$ su--orted. In this docuent, the ter integer is eant to

generall$ include 7oth signed and unsigned integers. 6nsigned integers have eactl$ (! 7its o% -recision.

#igned integers use (! 7its, including a sign 7it, in twos co-leent %or. )-erations resulting in

over%low or under%low will not cause an$ ece-tion, nor will the$ saturate, rather the$ will wra-C to $ield

the low;order (! 7its o% the result.

Integers are declared and o-tionall$ initiali?ed with integer e-ressions, as in the %ollowing ea-le:

int i/ 0 . 12 ** default integer literal t&pe is int

uint 3 . 4u ** +u, esta$lis5es t5e t&pe as uint

1


25/123


0iteral integer constants can 7e e-ressed in decial F7ase 1'G, octal F7ase 5G, or headecial F7ase 1G

as %ollows.

integer-constant :

#ecima'-constant integer-su))i%ot

octa'-constant integer-su))i%ot

he%a#ecima'-constant integer-su))i%ot

integer-su))i%: one o%

4 S

#ecima'-constant :

nonero-#igit

#ecima'-constant #igit

octa'-constant :

0

octa'-constant octa'-#igit

he%a#ecima'-constant :

'he%a#ecima'-#igit

'Whe%a#ecima'-#igit

he%a#ecima'-constant he%a#ecima'-#igit

#igit :

0

nonero-#igit

nonero-#igit : one o%

1 < B X Y [ 9

octa'-#igit one o%

0 1 < B X Y

he%a#ecima'-#igitone o%

0 1 < B X Y [ 9

a > c d e 3

A E C D I J


26/123


%.1.% ,loats

3loats are availa7le %or use in a variet$ o% scalar calculations. 3loating;-oint varia7les are de%ined as in the

%ollowing ea-le:

float a/ $ . '67

As an in-ut value to one o% the -rocessing units, a %loating;-oint varia7le is e-ected to atch the IEEE

4&* single -recision %loating;-oint de%inition %or -recision and d$naic range. 3loating;-oint varia7les

within a shader are also encoded according to the IEEE 4&* s-eci%ication %or single;-recision %loating;

-oint values. +owever, it is not re=uired that the -recision o% internal -rocessing atch the IEEE 4&*

%loating;-oint s-eci%ication %or %loating;-oint o-erations, 7ut the guidelines %or -recision esta7lished 7$

the )-en/0 /ra-hics #$ste #-eci%ication ust 7e et. #iilarl$, treatent o% conditions such as divide

7$ ' a$ lead to an uns-eci%ied result, 7ut in no case should such a condition lead to the interru-tion or

terination o% -rocessing. /enerall$, there are no signaling


27/123


%.1. Vectors

he )-en/0 #hading 0anguage includes data t$-es %or generic !;, (;, and *;co-onent vectors o%

%loating;-oint values, integers, or Booleans. 3loating;-oint vector varia7les can 7e used to store colors,

norals, -ositions, teture coordinates, teture looku- results and the like. Boolean vectors can 7e used

%or co-onent;wise co-arisons o% nueric vectors. #oe ea-les o% vector declaration are:

ve%2 tex%oord'/ tex%oord2

ve%4 position

ve%1 m&R!-8

ive%2 textureLoo3up

$ve%4 less

Initiali?ation o% vectors can 7e done with constructors, which are discussed shortl$.

%.1.( 5atrices

he )-en/0 #hading 0anguage has 7uilt;in t$-es %or !!, !(, !*, (!, ((, (*, *!, *(, and **atrices o% %loating;-oint nu7ers. he %irst nu7er in the t$-e is the nu7er o% coluns, the second is

the nu7er o% rows. Ea-le atri declarations:

mat2 mat2

mat4 opt9atrix

mat1 vie:/ pro0e%tion

mat1x1 vie: ** an alternate :a& of de%laring a mat1

mat4x2 m ** a matrix :it5 4 %olumns and 2 ro:s

Initiali?ation o% atri values is done with constructors Fdescri7ed in section &.* "onstructorsC G in

colun;aTor order.

%.1. Samplers

#a-ler t$-es Fe.g., sam7lerDG are e%%ectivel$ o-a=ue handles to tetures and their %ilters. he$ are

used with the 7uilt;in teture %unctions Fdescri7ed in section 5.4 eture 0ooku- 3unctionsC G to s-eci%$

which teture to access and how it is to 7e %iltered. he$ can onl$ 7e declared as %unction -araeters or

4ni3ormvaria7les Fsee section *.(.& 6ni%orC G. Ece-t %or arra$ indeing, structure %ield selection, and

-arentheses, sa-lers are not allowed to 7e o-erands in e-ressions. #a-lers aggregated into arra$s

within a shader Fusing s=uare 7rackets $ %G can onl$ 7e indeed with integral constant e-ressions Fsee

section *.(.( "onstant E-ressionsCG. #a-lers cannot 7e treated as l;values hence cannot 7e used as

o4t or ino4t %unction -araeters, nor can the$ 7e assigned into. As uni%ors, the$ are initiali?ed onl$

with the )-en/0 A2I the$ cannot 7e declared with an initiali?er in a shader. As %unction -araeters,

onl$ sa-lers a$ 7e -assed to sa-lers o% atching t$-e. his ena7les consistenc$ checking 7etween

shader teture accesses and )-en/0 teture state 7e%ore a shader is run.

21


28/123


%.1.3 Structures

6ser;de%ined t$-es can 7e created 7$ aggregating other alread$ de%ined t$-es into a structure using the

str4ctke$word. 3or ea-le,

stru%t lig5t ;

float intensit&

ve%4 position

< lig5tVar

In this ea-le, 'ight7ecoes the nae o% the new t$-e, and 'ightVar7ecoes a varia7le o% t$-e 'ight.

o declare varia7les o% the new t$-e, use its nae Fwithout the ke$word str4ctG.

lig5t lig5tVar2

8ore %orall$, structures are declared as %ollows. +owever, the co-lete correct graar is as given in

section 9 #hading 0anguage /raarC .

struct-#e)inition :ua'i)ier

ot str4ctname

ot(mem&er-'ist )#ec'arators

ot

mem&er-'ist :

mem&er-#ec'aration

mem&er-#ec'aration mem&er-'ist

mem&er-#ec'aration :

&asic-t(e #ec'arators

where name7ecoes the user;de%ined t$-e, and can 7e used to declare varia7les to 7e o% this new t$-e.

he nameshares the sae nae s-ace as other varia7les, t$-es, and %unctions. All -reviousl$ visi7le

varia7les, t$-es, constructors, or %unctions with that nae are hidden. he o-tional ua'i)ieronl$ a--lies

to an$ #ec'arators, and is not -art o% the t$-e 7eing de%ined %or name.

#tructures ust have at least one e7er declaration. 8e7er declarators a$ contain -recision

=uali%iers, 7ut a$ not contain an$ other =uali%iers. Bit %ields are not su--orted. 8e7er t$-es ust 7e

alread$ de%ined Fthere are no %orward re%erencesG. 8e7er declarations cannot contain initiali?ers.

8e7er declarators can contain arra$s. #uch arra$s ust have a si?e s-eci%ied, and the si?e ust 7e an

integral constant e-ression thats greater than ?ero Fsee section *.(.( "onstant E-ressionsCG. Each

level o% structure has its own nae s-ace %or naes given in e7er declarators such naes need onl$

7e uni=ue within that nae s-ace.

22


29/123


Anon$ous structures are not su--orted. E7edded structure de%initions are not su--orted.

stru%t S ; float f


30/123


and as an alternate wa$ o% declaring a varia7le or %unction -araeter.

float>7? a

It is an error to declare arra$s o% arra$s:

float a>7?>4? ** illegal

float>7? a>4? ** illegal

Arra$s can have initiali?ers %ored %ro arra$ constructors:

float a>7? . float>7?461/ 162/ 76A/ 762/ '6')

float a>7? . float>?461/ 162/ 76A/ 762/ '6') ** same t5ing

6nsi?ed arra$s can 7e e-licitl$ si?ed 7$ an initiali?er at declaration tie:

float a>7?

666

float $>? . a ** $ is expli%itl& si"e 7

float $>7? . a ** means t5e same t5ing

+owever, i-licitl$ si?ed arra$s cannot 7e assigned to.


31/123


%.1.1! Implicit Con#ersions

In soe situations, an e-ression and its t$-e will 7e i-licitl$ converted to a di%%erent t$-e. he

%ollowing ta7le shows all allowed i-licit conversions:

Type of e*pression Can be implicitly con#erted to

int

4int

3loat

ivec4vec

vec

ivec4te de-recatedlinkage 7etween a verte shader and )-en/0 %or -er;vertedata

4ni3orm value does not change across the -riitive 7eing -rocessed, uni%ors%or the linkage 7etween a shader, )-en/0, and the a--lication

var?ingcentroid var?ing

de-recated linkage 7etween a verte shader and a %ragent shader %orinter-olated data

)ut-uts %ro shader Fo4tG and in-uts to a shader FinG can 7e %urther =uali%ied with one o% these

inter-olation =uali%iers

7ualifier 5eaning

smoot@ -ers-ective correct inter-olation

3lat no inter-olation

no7ers7ective linear inter-olation

hese inter-olation =uali%iers a$ onl$ -recede the =uali%iers in, centroid in, o4t, or centroid o4t in a

declaration. he$ do not a--l$ to the de-recated storage =uali%iers var?ing or centroid var?ing. he$

also do not a--l$ to in-uts into a verte shader or out-uts %ro a %ragent shader.

0ocal varia7les can onl$ use the const storage =uali%ier.

3unction -araeters can use const,in, ando4t =uali%iers, 7ut asarameter ua'i)iers. 2araeter

=uali%iers are discussed in section .1.1 3unction "alling "onventionsC.

3unction return t$-es and structure %ields do not use storage =uali%iers.

Data t$-es %or counication %ro one run o% a shader eecuta7le to its net run Fto counicate

7etween %ragents or 7etween verticesG do not eist. his would -revent -arallel eecution o% the sae

shader eecuta7le on ulti-le vertices or %ragents.

27


34/123


35/123


"onstant e-ressions will 7e evaluated in an invariant wa$ so as to create the sae value in ulti-le

shaders when the sae constant e-ressions a--ear in those shaders. #ee section *..1he Invariant

uali%ierC %or ore details on how to create invariant e-ressions.

%.".% Inputs

#hader in-ut varia7les are declared with the in storage =uali%ier or the centroid instorage =uali%ier. he$

%or the in-ut inter%ace 7etween -revious stages o% the )-en/0 -i-eline and the declaring shader. In-ut

varia7les ust 7e declared at glo7al sco-e. Values %ro the -revious -i-eline stage are co-ied into in-ut

varia7les at the 7eginning o% shader eecution. Varia7les declared as in or centroid in a$ not 7e written

to during shader eecution. )nl$ the in-ut varia7les that are actuall$ read need to 7e written 7$ the

-revious stage it is allowed to have su-er%luous declarations o% in-ut varia7les.

#ee section 4 Built;in Varia7lesC %or a list o% the 7uilt;in in-ut naes.

Verte shader in-ut varia7les For attri7utesG receive -er;verte data. he$ are declared in a verte shader

with the in =uali%ier or the de-recated attri>4te=uali%ier. It is an error to use centroid in or inter-olation

=uali%iers in a verte shader in-ut. he values co-ied in are esta7lished 7$ the )-en/0 A2I or throughthe use o% the la$out identi%ier 'ocation. It is an error to use attri>4tein a non;verte shader. Verte

shader in-uts can onl$ 7e 3loat, %loating;-oint vectors, atrices, signed and unsigned integers and integer

vectors. Verte shader in-uts can also %or arra$s o% these t$-es, 7ut not structures.

Ea-le declarations in a verte shader:

in ve%1 position

in ve%4 normal

in ve%2 texCoord>1?

It is e-ected that gra-hics hardware will have a sall nu7er o% %ied vector locations %or -assing verte

in-uts. here%ore, the )-en/0 #hading language de%ines each non;atri in-ut varia7le as taking u- one

such vector location. here is an i-leentation de-endent liit on the nu7er o% locations that can 7e

used, and i% this is eceeded it will cause a link error. FDeclared in-ut varia7les that are not staticall$ useddo not count against this liit.G A scalar in-ut counts the sae aount against this liit as a vecB, so

a--lications a$ want to consider -acking grou-s o% %our unrelated %loat in-uts together into a vector to

7etter utili?e the ca-a7ilities o% the underl$ing hardware. A atri in-ut will use u- ulti-le locations.

he nu7er o% locations used will e=ual the nu7er o% coluns in the atri.

/eoetr$ shader in-ut varia7les get the -er;verte values written out 7$ verte shader out-ut varia7les o%

the sae naes. #ince a geoetr$ shader o-erates on a set o% vertices, each in-ut var$ing varia7le For

in-ut 7lock, see inter%ace 7locks 7elowG needs to 7e declared as an arra$. 3or ea-le,

in float foo>? ** geometr& s5ader input for vertex +out float foo,

Each eleent o% such an arra$ corres-onds to one verte o% the -riitive 7eing -rocessed. Each arra$ can

o-tionall$ have a si?e declared. he arra$ si?e will 7e set 7$, For i% -rovided ust 7e consistent withG the

in-ut la?o4tdeclarationFsG esta7lishing the t$-e o% in-ut -riitive, as descri7ed later in section *.(.5.1

In-ut 0a$out uali%iersC.

2!


36/123


3or the inter%ace 7etween a verte shader and a geoetr$ shader, verte shader out-ut varia7les and

geoetr$ shader in-ut varia7les o% the sae nae ust atch in t$-e and =uali%ication, ece-t that the

verte shader nae cannot 7e declared as an arra$ while the geoetr$ shader nae ust 7e declared as an

arra$. )therwise, a link error will occur.

I% the out-ut o% a verte shader is itsel% an arra$ to 7e consued 7$ a geoetr$ shader, then it ust a--ear

in an out-ut 7lock Fsee inter%ace 7locks 7elowG in the verte shader and in an in-ut 7lock in the geoetr$

shader with a 7lock instance nae declared as an arra$. his is re=uired %or arra$s out-ut %ro a verte

shader 7ecause two;diensional arra$s are not su--orted.

3ragent shader in-uts get -er;%ragent values, t$-icall$ inter-olated %ro a -revious stages out-uts.

he$ are declared in %ragent shaders with the in storage =uali%ier, the centroid in storage =uali%ier, or

the de-recated var?ingand centroid var?ing storage =uali%iers. 3ragent in-uts can onl$ 7e signed and

unsigned integers and integer vectors, 3loat, %loating;-oint vectors, atrices, or arra$s or structures o%

these. 3ragent shader in-uts that are signed or unsigned integers or integer vectors ust 7e =uali%ied

with the inter-olation =uali%ier 3lat.

3ragent in-uts are declared as in the %ollowing ea-les:

in ve%4 normal

%entroid in ve%2 TexCoord

invariant %entroid in ve%1 Color

noperspe%tive in float temperature

flat in ve%4 m&Color

noperspe%tive %entroid in ve%2 m&TexCoord

I% a geoetr$ shader is not -resent in a -rogra, 7ut a verte and %ragent shader are -resent, then the

out-ut o% the verte shader and the in-ut o% the %ragent shader %or an inter%ace. 3or this inter%ace,

verte shader out-ut varia7les and %ragent shader in-ut varia7les o% the sae nae ust atch in t$-e

and =uali%ication Fother than o4t atching to inG.

%.". 4niform

he 4ni3orm =uali%ier is used to declare glo7al varia7les whose values are the sae across the entire

-riitive 7eing -rocessed. All 4ni3ormvaria7les are read;onl$ and are initiali?ed eternall$ either at link

tie or through the A2I. he link tie initial value is either the value o% the varia7les initiali?er, i%

-resent, or ' i% no initiali?er is -resent. #a-ler t$-es cannot have initiali?ers.

Ea-le declarations are:

uniform ve%1 lig5t@osition

uniform ve%4 %olor . ve%4A6D/ A6D/ A62) ** value assigned at lin3 time

he 4ni3orm=uali%ier can 7e used with an$ o% the 7asic data t$-es, or when declaring a varia7le whose

t$-e is a structure, or an arra$ o% an$ o% these.

here is an i-leentation de-endent liit on the aount o% storage %or uni%ors that can 7e used %or

each t$-e o% shader and i% this is eceeded it will cause a co-ile;tie or link;tie error. 6ni%or

varia7les that are declared 7ut not used do not count against this liit. he nu7er o% user;de%ined

uni%or varia7les and the nu7er o% 7uilt;in uni%or varia7les that are used within a shader are added

together to deterine whether availa7le uni%or storage has 7een eceeded.

3"


37/123


I% ulti-le shaders are linked together, then the$ will share a single glo7al uni%or nae s-ace, including

within a language as well as across languages. +ence, the t$-es and initiali?ers o% uni%or varia7les with

the sae nae ust atch across all shaders that are linked into a single -rogra.

It is legal %or soe shaders to -rovide an initiali?er %or a -articular uni%or varia7le, while another shader

does not, 7ut all -rovided initiali?ers ust 7e e=ual.

%.".( Outputs

#hader out-ut varia7les are declared with the o4t or centroid o4t storage =uali%iers. he$ %or the

out-ut inter%ace 7etween the declaring shader and the su7se=uent stages o% the )-en/0 -i-eline. )ut-ut

varia7les ust 7e declared at glo7al sco-e. During shader eecution the$ will 7ehave as noral

un=uali%ied glo7al varia7les. heir values are co-ied out to the su7se=uent -i-eline stage on shader eit.

)nl$ out-ut varia7les that are read 7$ the su7se=uent -i-eline stage need to 7e written it is allowed to

have su-er%luous declarations o% out-ut varia7les.

here is notan ino4tstorage =uali%ier at glo7al sco-e %or declaring a single varia7le nae as 7oth in-ut

and out-ut to a shader. )ut-ut varia7les ust 7e declared with di%%erent naes than in-ut varia7les.+owever, nesting an in-ut or out-ut inside an inter%ace 7lock with an instance nae allows the sae

naes with one re%erenced through a 7lock instance nae.

Verte and geoetr$ out-ut varia7les out-ut -er;verte data and are declared using the o4tstorage

=uali%ier, the centroid o4tstorage =uali%ier, or the de-recated var?ingstorage =uali%ier. he$ can onl$ 7e

3loat, %loating;-oint vectors, atrices, signed or unsigned integers or integer vectors, or arra$s or

structures o% an$ these.

Individual verte and geoetr$ out-uts are declared as in the %ollowing ea-les:

out ve%4 normal

%entroid out ve%2 TexCoord

invariant %entroid out ve%1 Color

noperspe%tive out float temperature ** var&ing is depre%atedflat out ve%4 m&Color

noperspe%tive %entroid out ve%2 m&TexCoord

hese can also a--ear in inter%ace 7locks, as descri7ed in the section *.(.4 Inter%ace BlocksC. Inter%ace

7locks allow si-ler addition o% arra$s to the inter%ace %ro verte to geoetr$ shader. he$ also allow a

%ragent shader to have the sae in-ut inter%ace as a geoetr$ shader %or a given verte shader.

3ragent out-uts out-ut -er;%ragent data and are declared using the o4t storage =uali%ier. It is an error

to use centroid o4t in a %ragent shader. 3ragent out-uts can onl$ 7e 3loat, %loating;-oint vectors,

signed or unsigned integers or integer vectors, or arra$s o% an$ these. 8atrices and structures cannot 7e

out-ut. 3ragent out-uts are declared as in the %ollowing ea-les:

out ve%1 FragmentColor

out uint Luminosit&

31


38/123


%.". Interface -loc0s

In-ut, out-ut, and uni%or varia7le declarations can 7e grou-ed into naed inter%ace 7locks to -rovide

coarser granularit$ 7acking than is achieva7le with individual declarations. he$ can have an o-tional

instance nae, used in the shader to re%erence their e7ers. An out-ut 7lock o% one -rograa7le

stage is 7acked 7$ a corres-onding in-ut 7lock in the su7se=uent -rograa7le stage. A uni%or 7lock is

7acked 7$ the a--lication with a 7u%%er o7Tect. It is illegal to have an in-ut 7lock in a verte shader or an

out-ut 7lock in a %ragent shader these uses are reserved %or %uture use.

An inter%ace 7lock is started 7$ an in, o4t, or 4ni3orm ke$word, %ollowed 7$ a 7lock nae, %ollowed 7$

an o-en curl$ 7race F ( G as %ollows:

inter)ace-&'oc/ :

'a(out-ua'i)iero7t inter)ace-ua'i)ier &'oc/-name (mem&er-'ist )instance-nameo7t

'a(out-ua'i)ier :

la?o4t & 'a(out-ua'i)ier-i#-'ist'

inter)ace-ua'i)ier :in

o4t

4ni3orm

'a(out-ua'i)ier-i#-'ist

coa se-arated list o% 'a(out-ua'i)ier-i#

mem&er-'ist :

mem&er-#ec'aration

mem&er-#ec'aration mem&er-'ist

mem&er-#ec'aration :

'a(out-ua'i)iero7t ua'i)ierso7t t(e #ec'arators

instance-name :

i#enti)ier

i#enti)ier 7

i#enti)ier integra'-constant-e%ression 7

Each o% the a7ove eleents is discussed 7elow, with the ece-tion o% la$out =uali%iers F 'a(out-ua'i)ier5,

which are de%ined in the net section.

3irst, an ea-le,

uniform Transform ;

mat1 9odelVie:9atrix

mat1 9odelVie:@ro0e%tion9atrix

uniform mat4 Normal9atrix ** allo:ed restatement of =ualifier

float eformation


39/123


$-es and declarators are the sae as %or other in-ut, out-ut, and uni%or varia7le declarations outside

7locks, with these ece-tions:

initiali?ers are not allowed

sa-ler t$-es are not allowed

structure de%initions cannot 7e nested inside a 7lock

)therwise, 7uilt;in t$-es, -reviousl$ declared structures, and arra$s o% these are allowed as the t$-e o% a

declarator in the sae anner the$ are allowed outside a 7lock.

I% no o-tional =uali%ier is used in a e7er;declaration, the =uali%ication o% the varia7le is Tust in, o4t, or

4ni3ormas deterined 7$ inter)ace-ua'i)ier. I% o-tional =uali%iers are used, the$ can include

inter-olation and storage =uali%iers and the$ ust declare an in-ut, out-ut, or uni%or varia7le consistent

with the inter%ace =uali%ier o% the 7lock: In-ut varia7les, out-ut varia7les, and uni%or varia7les can onl$

7e in in7locks, o4t7locks, and 4ni3orm7locks, res-ectivel$. Re-eating the in, o4t, or 4ni3orm

inter%ace =uali%ier %or a e7ers storage =uali%ier is o-tional. Declarations using the de-recated

attri>4te and var?ing=uali%iers are not allowed. 3or ea-le,

in 9aterial ;

smoot5 in ve%1 Color' ** legal/ input inside in $lo%3

smoot5 ve%1 Color2 ** legal/ BinB in5erited from Bin 9aterialB

ve%2 TexCoord ** legal/ TexCoord is an input

uniform float 8tten ** illegal/ mismat%5ed interfa%es

var&ing ve%2 TexCoord2**illegal/ depre%ated 3e&:ords donBt get ne: uses


40/123


I% an instance nae Finstance-nameGis not used, the naes declared inside the 7lock are sco-ed at the

glo7al level and accessed as i% the$ were declared outside the 7lock. I% an instance nae Finstance-nameG

is used, then it -uts all the e7ers inside a sco-e within its own nae s-ace, accessed with the %ield

selector F . G o-erator Fanalogousl$ to structuresG. 3or ea-le,

in Lig5t ;

ve%1 Lig5t@os

ve%4 Lig5tColor

1?

666

666 . transforms>2?69odelVie:9atrix ** s5ader a%%ess of instan%e 2

** 8@I uses +Transform69odelVie:9atrix, to =uer& an offset or ot5er =uer&

3or uni%or 7locks declared as an arra$, each individual arra$ eleent corres-onds to a se-arate 7u%%ero7Tect 7acking one instance o% the 7lock. As the arra$ si?e indicates the nu7er o% 7u%%er o7Tects needed,

uni%or 7lock arra$ declarations ust s-eci%$ an arra$ si?e. All indees used to inde a uni%or 7lock

arra$ ust 7e integral constant e-ressions.

34


41/123


hen using )-en/0 A2I entr$ -oints to identi%$ the nae o% an individual 7lock in an arra$ o% 7locks,

the nae string ust include an arra$ inde Fe.g., Trans)orm27G. hen using )-en/0 A2I entr$ -oints

to re%er to o%%sets or other characteristics o% a 7lock e7er, an arra$ inde ust not 7e s-eci%ied Fe.g.,

Trans)orm.Mo#e'VieMatri%G.

/eoetr$ shader in-ut 7locks ust 7e declared as arra$s and %ollow the arra$ declaration and linking

rules %or all geoetr$ shader in-uts. All other in-ut and out-ut 7lock arra$s ust s-eci%$ an arra$ si?e.

here is an i-leentation de-endent liit on the nu7er o% uni%or 7locks that can 7e used -er stage.

I% this liit is eceeded, it will cause a link error.

%.".3 Layout 7ualifiers

0a$out =uali%iers can a--ear in several %ors o% declaration. he$ can a--ear as -art o% an inter%ace

7lock de%inition or 7lock e7er, as shown in the graar in the -revious section. he$ can also a--ear

with Tust an inter%ace =uali%ier to esta7lish la$outs o% other declarations ade with that inter%ace =uali%ier:

'a(out-ua'i)ierinter)ace-ua'i)ier

)r, the$ can a--ear with an individual varia7le declared with an inter%ace =uali%ier:

'a(out-ua'i)ierinter)ace-ua'i)ier #ec'aration

Declarations o% la$outs can onl$ 7e ade at glo7al sco-e, and onl$ where indicated in the %ollowing

su7sections their details are s-eci%ic to what the inter%ace =uali%ier is, and are discussed individuall$.

As shown in the -revious section, 'a(out-ua'i)ier e-ands to

'a(out-ua'i)ier :

la?o4t & 'a(out-ua'i)ier-i#-'ist'

he tokens in an$ 'a(out-ua'i)ier-i#-'istare identi%iers, not ke$words. /enerall$, the$ can 7e listed in

an$ order. )rder;de-endent eanings eist onl$ i% e-licitl$ called out 7elow. #iilarl$, these identi%iers

are not case sensitive, unless e-licitl$ noted otherwise.

%.".3.1 Input Layout 7ualifiers

Verte shaders allow in-ut la$out =uali%iers on in-ut varia7le declarations. he la$out =uali%ier identi%ier

%or verte shader in-uts is:

'a(out-ua'i)ier-i#

location integer-constant

)nl$ one arguent is acce-ted. 3or ea-le,

la&outlo%ation . 4) in ve%1 normal

will esta7lish that the verte shader in-ut norma' is co-ied in %ro vector location nu7er (.

I% the declared in-ut is an arra$, it will 7e assigned consecutive locations starting with the location

s-eci%ied. 3or ea-le,

la&outlo%ation . ) in ve%1 %olors>4?

will esta7lish that the verte shader in-ut co'orsis co-ied in %ro vector location nu7ers , 4, and 5.

35


42/123


I% an in-ut varia7le with no location assigned in the shader tet has a location s-eci%ied through the

)-en/0 A2I, the A2I;assigned location will 7e used. )therwise, such varia7les will 7e assigned a

location 7$ the linker. #ee section !.11.* Verte Attri7utesC o% the )-en/0 /ra-hics #$ste

#-eci%ication %or ore details. A link error will occur i% an in-ut varia7le is declared in ulti-le verteshaders with con%licting locations.

/eoetr$ shaders allow in-ut la$out =uali%iers onl$ on the inter%ace =uali%ier in, not on an in-ut 7lock,

7lock e7er, or varia7le. he la$out =uali%ier identi%iers %or geoetr$ shader in-uts are

'a(out-ua'i)ier-i#

7oints

lines

lines5adGacenc?

triangles

triangles5adGacenc?

)nl$ one arguent is acce-ted. 3or ea-le,

la&outtriangles) in

will esta7lish that all in-uts to the geoetr$ shader are triangles.

At least one geoetr$ shader Fco-ilation unitG in a -rogra ust declare an in-ut la$out, and all

geoetr$ shader in-ut la$out declarations in a -rogra ust declare the sae la$out. It is not re=uired

that all geoetr$ shaders in a -rogra declare an in-ut la$out.

All geoetr$ shader in-ut unsi?ed arra$ declarations will 7e si?ed 7$ an earlier in-ut la$out =uali%ier,

when -resent, as -er the %ollowing ta7le.

;a?o4t 8ize o3 Ln74t Arra?s

-oints 1

lines !

lines>adTacenc$ *

triangles (

triangles>adTacenc$

he intrinsicall$ declared in-ut arra$g'*in7will also 7e si?ed 7$ an$ in-ut la$out declaration. +ence,

the e-ression

gl_in6lengt5)

will return the value %ro the ta7le a7ove.

3or in-uts declared without an arra$ si?e, including intrinsicall$ declared in-uts Fi.e.,g'*inG, a la$out ust

7e declared 7e%ore an$ use o% the ethod 'ength45or other arra$ use re=uiring its si?e 7e known.

36


43/123


44/123


Redeclaringg'*rag8oor# with origin5477er5le3t and@or 7i=el5center5integer=uali%iers onl$ a%%ects

g'*rag8oor#.% and g'*rag8oor#.(. It has no a%%ect on rasteri?ation, trans%oration, or an$ other -art

o% the )-en/0 -i-eline or language %eatures.

%.".3.2 Output Layout 7ualifiers

Verte shaders cannot have out-ut la$out =uali%iers.

3ragent shaders allow out-ut la$out =uali%iers onl$ on the inter%ace =uali%ier o4t. he la$out =uali%ier

identi%ier %or %ragent shader out-uts is:

'a(out-ua'i)ier-i#

location integer-constant

inde= integer-constant

Each o% these =uali%iers a$ a--ear at ost once. I% inde= is s-eci%ied, location ust also 7e s-eci%ied.

I% inde= is not s-eci%ied, the value ' is used. 3or ea-le,

la&outlo%ation . 4) out ve%1 %olor

will esta7lish that the %ragent shader out-ut co'or is co-ied out to %ragent color ( as the %irst Finde

?eroG in-ut to the 7lend e=uation. And,

la&outlo%ation . 4/ index . ') out ve%1 fa%tor

will esta7lish that the %ragent shader out-ut)actoris co-ied out to %ragent color ( as the second Finde

oneG in-ut to the 7lend e=uation.

I% the naed %ragent shader out-ut is an arra$, it will 7e assigned consecutive locations starting with the

location s-eci%ied. 3or ea-le,

la&outlo%ation . 2) out ve%1 %olors>4?

will esta7lish that co'orsis co-ied out to vector location nu7ers !, (, and *.

I% an out-ut varia7le with no location or inde assigned in the shader tet has a location s-eci%ied through

the )-en/0 A2I, the A2I;assigned location will 7e used. )therwise, such varia7les will 7e assigned a

location 7$ the linker. All such assignents will have a color inde o% ?ero. #ee section (.9.! #hader

EecutionC o% the )-en/0 /ra-hics #$ste #-eci%ication %or ore details. A link error will occur i% an

in-ut varia7le is declared in ulti-le verte shaders with con%licting location or inde values.

/eoetr$ shaders can have out-ut la$out =uali%iers onl$ on the inter%ace =uali%ier o4t, not on an out-ut

7lock or varia7le declaration.

he la$out =uali%ier identi%iers %or geoetr$ shader out-uts are

'a(out-ua'i)ier-i#

7ointsline5stri7

triangle5stri7

ma=5verticesinteger-constant

3


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)ne declaration can declare either a -riitive t$-e F7oints,line5stri7, ortriangle5stri7G, or

ma=5vertices, or 7oth. 6se ma=5vertices to declare the aiu nu7er o% vertices this shader will

ever eit in a single eecution. 3or ea-le,

la&outtriangle_strip/ max_verti%es . A) out ** order does not matter

la&outmax_verti%es . A) out ** rede%laration o3a&

la&outtriangle_strip) out ** rede%laration o3a&

la&outpoints) out ** error/ %ontradi%ts triangle_strip

la&outmax_verti%es . 4A) out ** error/ %ontradi%ts A

these will esta7lish that all out-uts %ro the geoetr$ shader are triangles and at ost ' vertices will 7e

eitted 7$ the shader. It is an error %or the aiu nu7er o% vertices to 7e greater than

gl5Fa=:eometr?P4t74tTertices.

All geoetr$ shader out-ut la$out declarations in a -rogra ust declare the sae la$out and sae value

%or ma=5vertices. I% geoetr$ shaders are in a -rogra, there ust 7e at least one geoetr$ out-ut

la$out declaration soewhere in the -rogra, 7ut not all geoetr$ shaders Fco-ilation unitsG are

re=uired to declare it.

%.".3." 4niform -loc0 Layout 7ualifiers

0a$out =uali%iers can 7e used %or uni%or 7locks, 7ut not %or non;7lock uni%or declarations. he la$out

=uali%ier identi%iers %or uni%or 7locks are

'a(out-ua'i)ier-i#

s@ared

7acked

std1B0

row5maGor

col4mn5maGor


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6ni%or 7locks can 7e declared with o-tional la$out =uali%iers, and so can their individual e7er

declarations. #uch 7lock la$out =uali%ication is sco-ed onl$ to the content o% the 7lock. As with glo7al

la$out declarations, 7lock la$out =uali%ication %irst inherits %ro the current de%ault =uali%ication and then

overrides it. #iilarl$, individual e7er la$out =uali%ication is sco-ed Tust to the e7er declaration,and inherits %ro and overrides the 7locks =uali%ication.

heshare# =uali%ier overrides onl$ thest#190 andac/e# =uali%iers other =uali%iers are inherited. he

co-iler@linker will ensure that ulti-le -rogras and -rograa7le stages containing this de%inition

will share the sae eor$ la$out %or this 7lock, as long as the$ also atched in their ro*maor and@or

co'umn*maor =uali%ications. his allows use o% the sae 7u%%er to 7ack the sae 7lock de%inition across

di%%erent -rogras.

heac/e# =uali%ier overrides onl$st#190 andshare# other =uali%iers are inherited. henac/e# is

used, no sharea7le la$out is guaranteed. he co-iler and linker can o-tii?e eor$ use 7ased on what

varia7les activel$ get used and on other criteria. )%%sets ust 7e =ueried, as there is no other wa$ o%

guaranteeing where Fand whichG varia7les reside within the 7lock. Atte-ts to share a -acked uni%or

7lock across -rogras or stages will generall$ %ail. +owever, i-leentations a$ aid a--lication

anageent o% -acked 7locks 7$ using canonical la$outs %or -acked 7locks.

hest#190 =uali%ier overrides onl$ theac/e# andshare# =uali%iers other =uali%iers are inherited. he

la$out is e-licitl$ deterined 7$ this, as descri7ed in section !.11.& 6ni%or Varia7lesC under

#tandard 6ni%or Block 0a$outC o% the )-en/0 /ra-hics #$ste #-eci%ication. +ence, as inshare#

a7ove, the resulting la$out is sharea7le across -rogras.

0a$out =uali%iers on e7er declarations cannot use theshare#,ac/e#,orst#190 =uali%iers. hese can

onl$ 7e used at glo7al sco-e or on a 7lock declaration.

he ro*maor =uali%ier overrides onl$ the co'umn*maor=uali%ier other =uali%iers are inherited. It onl$

a%%ects the la$out o% atrices. Eleents within a atri row will 7e contiguous in eor$.

he co'umn*maor =uali%ier overrides onl$ the ro*maor=uali%ier other =uali%iers are inherited. It onl$

a%%ects the la$out o% atrices. Eleents within a atri colun will 7e contiguous in eor$.

hen ulti-le arguents are listed in a la?o4t declaration, the a%%ect will 7e the sae as i% the$ were

declared one at a tie, in order %ro le%t to right, each in turn inheriting %ro and overriding the result

%ro the -revious =uali%ication.

4"


47/123


3or ea-le

la&outro:_ma0or/ %olumn_ma0or)

results in the =uali%ication 7eing co'umn*maor. )ther ea-les:

la&outs5ared/ ro:_ma0or) uniform ** default is no: s5ared and ro:_ma0or

la&outstd'1A) uniform Transform ; ** la&out of t5is $lo%3 is std'1A

mat1 9' ** ro:_ma0or

la&out%olumn_ma0or) mat1 92 ** %olumn ma0or

mat4 N' ** ro:_ma0or


48/123


49/123


50/123


51/123


%.(.1 The In#ariant 7ualifier

o ensure that a -articular out-ut varia7le is invariant, it is necessar$ to use the invariant=uali%ier. It can

either 7e used to =uali%$ a -reviousl$ declared varia7le as 7eing invariant

invariant gl_@osition ** ma3e existing gl_@osition $e invariant

out ve%4 Color

invariant Color ** ma3e existing Color $e invariant

or as -art o% a declaration when a varia7le is declared

invariant %entroid out ve%4 Color

he invariant =uali%ier ust a--ear 7e%ore an$ inter-olation =uali%iers or storage =uali%iers when

co7ined with a declaration. )nl$ varia7les out-ut %ro a shader Fincluding those that are then in-ut to a

su7se=uent shaderG can 7e candidates %or invariance. his includes user;de%ined out-ut varia7les and the

7uilt;in out-ut varia7les. 3or varia7les leaving one shader and coing into another shader, the invariantke$word has to 7e used in 7oth shaders, or a link error will result.

In-ut or out-ut instance naes on 7locks are not used when redeclaring 7uilt;in varia7les.

he invariantke$word can 7e %ollowed 7$ a coa se-arated list o% -reviousl$ declared identi%iers. All

uses o% invariantust 7e at the glo7al sco-e, and 7e%ore an$ use o% the varia7les 7eing declared as

invariant.

o guarantee invariance o% a -articular out-ut varia7le across two -rogras, the %ollowing ust also 7e

true:

he out-ut varia7le is declared as invariant in 7oth -rogras.

he sae values ust 7e in-ut to all shader in-ut varia7les consued 7$ e-ressions and %low control

contri7uting to the value assigned to the out-ut varia7le.

he teture %orats, teel values, and teture %iltering are set the sae wa$ %or an$ teture %unction

calls contri7uting to the value o% the out-ut varia7le.

All in-ut values are all o-erated on in the sae wa$. All o-erations in the consuing e-ressions and

an$ interediate e-ressions ust 7e the sae, with the sae order o% o-erands and sae

associativit$, to give the sae order o% evaluation. Interediate varia7les and %unctions ust 7e

declared as the sae t$-e with the sae e-licit or i-licit -recision =uali%iers. An$ control %low

a%%ecting the out-ut value ust 7e the sae, and an$ e-ressions consued to deterine this control

%low ust also %ollow these invariance rules.

All the data %low and control %low leading to setting the invariant out-ut varia7le reside in a single

co-ilation unit.

Essentiall$, all the data %low and control %low leading to an invariant out-ut ust atch.

Initiall$, 7$ de%ault, all out-ut varia7les are allowed to 7e variant. o %orce all out-ut varia7les to 7e

invariant, use the -raga

45


52/123


#pragma ST!L invariantall)

7e%ore all declarations in a shader. I% this -raga is used a%ter the declaration o% an$ varia7les or

%unctions, then the set o% out-uts that 7ehave as invariant is unde%ined. It is an error to use this -raga ina %ragent shader.

/enerall$, invariance is ensured at the cost o% %lei7ilit$ in o-tii?ation, so -er%orance can 7e degraded

7$ use o% invariance. +ence, use o% this -raga is intended as a de7ug aid, to avoid individuall$ declaring

all out-ut varia7les as invariant.

%.(.2 In#ariance of Constant &*pressions

Invariance ust 7e guaranteed %or constant e-ressions. A -articular constant e-ression ust evaluate to

the sae result i% it a--ears again in the sae shader or a di%%erent shader. his includes the sae

e-ression a--earing two shaders o% the sae language or shaders o% two di%%erent languages.

"onstant e-ressions ust evaluate to the sae result when o-erated on as alread$ descri7ed a7ove %or

invariant varia7les.

%. Order of 7ualification

hen ulti-le =uali%ications are -resent, the$ ust %ollow a strict order. his order is as %ollows.

invariant-ua'i)ier intero'ation-ua'i)ier storage-ua'i)ier recision-ua'i)ier

storage-ua'i)ier arameter-ua'i)ier recision-ua'i)ier

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Operators and &*pressions

.1 Operators

he )-en/0 #hading 0anguage has the %ollowing o-erators.

+recedence Operator Class Operators ssociati#ity

1 FhighestG -arenthetical grou-ing & '


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5 Operators and ()pressions

.2 rray Operations

hese are now descri7ed in section &.4 #tructure and Arra$ )-erationsC.

." ,unction Calls

I% a %unction returns a value, then a call to that %unction a$ 7e used as an e-ression, whose t$-e will 7e

the t$-e that was used to declare or de%ine the %unction.

3unction de%initions and calling conventions are discussed in section .1 3unction De%initionsC .

.% Constructors

"onstructors use the %unction call s$nta, where the %unction nae is a t$-e, and the call akes an o7Tect

o% that t$-e. "onstructors are used the sae wa$ in 7oth initiali?ers and e-ressions. F#ee section 9

#hading 0anguage /raarC %or details.G he -araeters are used to initiali?e the constructed value.

"onstructors can 7e used to re=uest a data t$-e conversion to change %ro one scalar t$-e to another

scalar t$-e, or to 7uild larger t$-es out o% saller t$-es, or to reduce a larger t$-e to a saller t$-e.

In general, constructors are not 7uilt;in %unctions with -redeterined -rotot$-es. 3or arra$s and

structures, there ust 7e eactl$ one arguent in the constructor %or each eleent or %ield. 3or the other

t$-es, the arguents ust -rovide a su%%icient nu7er o% co-onents to -er%or the initiali?ation, and it

is an error to include so an$ arguents that the$ cannot all 7e used. Detailed rules %ollow. he

-rotot$-es actuall$ listed 7elow are erel$ a su7set o% ea-les.

.%.1 Con#ersion and Scalar Constructors

"onverting 7etween scalar t$-es is done as the %ollowing -rotot$-es indicate:

int$ool) ** %onverts a -oolean value to an int

intfloat) ** %onverts a float value to an int

float$ool) ** %onverts a -oolean value to a float

floatint) ** %onverts a signed integer value to a float

$oolfloat) ** %onverts a float value to a -oolean

$oolint) ** %onverts a signed integer value to a -oolean

uint$ool) ** %onverts a -oolean value to an unsigned integer

uintfloat) ** %onverts a float value to an unsigned integer

uintint) ** %onverts a signed integer value to an unsigned integer

intuint) ** %onverts an unsigned integer to a signed integer

$ooluint) ** %onverts an unsigned integer value to a -oolean value

floatuint) ** %onverts an unsigned integer value to a float value

hen constructors are used to convert a 3loatto an int or 4int, the %ractional -art o% the %loating;-oint

value is dro--ed. It is unde%ined to convert a negative %loating -oint value to an 4int.

hen a constructor is used to convert an int, 4int, or a 3loatto a >ool, ' and '.' are converted to 3alse,

and non;?ero values are converted to tr4e. hen a constructor is used to convert a >oolto an int, 4int,

or 3loat, 3alseis converted to ' or '.', and tr4eis converted to 1 or 1.'.

4


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he constructor int&4int'-reserves the 7it -attern in the arguent, which will change the arguents

value i% its sign 7it is set. he constructor 4int&int'-reserves the 7it -attern in the arguent, which will

change its value i% it is negative.

Identit$ constructors, like 3loatF3loatG are also legal, 7ut o% little use.

#calar constructors with non;scalar -araeters can 7e used to take the %irst eleent %ro a non;scalar.

3or ea-le, the constructor 3loatFvec


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#oe use%ul vector constructors are as %ollows:

ve%4float) ** initiali"es ea%5 %omponent of t5e ve%4 :it5 t5e float

ve%1ive%1) ** ma3es a ve%1 :it5 %omponent:ise %onversion

ve%1mat2) ** t5e ve%1 is %olumn A follo:ed $& %olumn '

ve%2float/ float) ** initiali"es a ve%2 :it5 2 floats

ive%4int/ int/ int) ** initiali"es an ive%4 :it5 4 ints

$ve%1int/ int/ float/ float) ** uses 1 -oolean %onversions

ve%2ve%4) ** drops t5e t5ird %omponent of a ve%4

ve%4ve%1) ** drops t5e fourt5 %omponent of a ve%1

ve%4ve%2/ float) ** ve%46x . ve%26x/ ve%46& . ve%26&/ ve%46" . float

ve%4float/ ve%2) ** ve%46x . float/ ve%46& . ve%26x/ ve%46" . ve%26&

ve%1ve%4/ float)

ve%1float/ ve%4)

ve%1ve%2/ ve%2)

#oe ea-les o% these are:

ve%1 %olor . ve%1A6A/ '6A/ A6A/ '6A)

ve%1 rg$a . ve%1'6A) ** sets ea%5 %omponent to '6A

ve%4 rg$ . ve%4%olor) ** drop t5e 1t5 %omponent

o initiali?e the diagonal o% a atri with all other eleents set to ?ero:

mat2float)

mat4float)

mat1float)

hat is, resu'ti77is set to the %loat arguent %or all i < and set to ' %or all i:.

5"


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o initiali?e a atri 7$ s-eci%$ing vectors or scalars, the co-onents are assigned to the atri eleents

in colun;aTor order.

mat2ve%2/ ve%2) ** one %olumn per argument

mat4ve%4/ ve%4/ ve%4) ** one %olumn per argument

mat1ve%1/ ve%1/ ve%1/ ve%1) ** one %olumn per argument

mat4x2ve%2/ ve%2/ ve%2) ** one %olumn per argument

mat2float/ float/ ** first %olumn

float/ float) ** se%ond %olumn

mat4float/ float/ float/ ** first %olumn

float/ float/ float/ ** se%ond %olumn

float/ float/ float) ** t5ird %olumn

mat1float/ float/ float/ float/ ** first %olumn

float/ float/ float/ float/ ** se%ond %olumn

float/ float/ float/ float/ ** t5ird %olumn float/ float/ float/ float) ** fourt5 %olumn

mat2x4ve%2/ float/ ** first %olumn

ve%2/ float) ** se%ond %olumn

A wide range o% other -ossi7ilities eist, to construct a atri %ro vectors and scalars, as long as enough

co-onents are -resent to initiali?e the atri. o construct a atri %ro a atri:

mat4x4mat1x1) ** ta3es t5e upperleft 4x4 of t5e mat1x1

mat2x4mat1x2) ** ta3es t5e upperleft 2x2 of t5e mat1x1/ last ro: is A/A

mat1x1mat4x4) ** puts t5e mat4x4 in t5e upperleft/ sets t5e lo:er rig5t

** %omponent to '/ and t5e rest to A

.%." Structure Constructors

)nce a structure is de%ined, and its t$-e is given a nae, a constructor is availa7le with the sae nae to

construct instances o% that structure. 3or ea-le:

stru%t lig5t ;

float intensit&

ve%4 position


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.%.% rray Constructors

Arra$ t$-es can also 7e used as constructor naes, which can then 7e used in e-ressions or initiali?ers.

3or ea-le,

%onst float %>4? . float>4?76A/ D62/ '6')

%onst float d>4? . float>?76A/ D62/ '6')

float g

666

float a>7? . float>7?g/ '/ g/ 264/ g)

float $>4?

$ . float>4?g/ g H '6A/ g H 26A)

here ust 7e eactl$ the sae nu7er o% ar

GLSL Specification 3.30.6.Clean

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